Effective biotechnology for reducing N2O-emissions from farmland: N2O-respiring bacteria vectored by organic waste

Farmed soils contribute to global warming primarily by N 2 O-emissions, and mitigation has proven difficult. However, a novel approach with promising results in the laboratory, exploits organic wastes both as substrates and vectors for strains of N 2 O-respiring bacteria (NRB), selected for their ability to survive in soil. Here we demonstrate a strong effect in field experiments: fertilization with waste from biogas-production, in which the strain Cloacibacterium sp. CB-01 had grown aerobically to ∼6*10 9 cells mL -1 , reduced N 2 O-emissions by 50-95 %. The strong and long-lasting effect of CB-01 is ascribed to it’s tenacity in soil, rather than its biokinetic parameters, which were inferior to other NRB-strains. Scaling up to EU level, we find that national anthropogenic N 2 O-emissions can be reduced by 5-20 %, and more if including other organic wastes. This opens an avenue for cost-effective reduction of N 2 O-emissions for which other mitigation options are currently lacking.